Drinking water and recreational water (water at beaches and other swimming facilities) should be tested on a regular basis, and the test results should be made available within a short period of time, in order to protect the public from harmful and contagious diseases.
Currently, most water sample tests are carried out in a laboratory environment away from water facilities or locations. Many methods and procedures currently used in routine microbiological analysis were developed over 100 years ago. They are labor intensive and time-consuming procedures both in operation and data collection. The results of such tests are typically not made available to the operators of these facilities for about 36 to 72 hours. Consequently, it is often not possible for operators of water facilities to take action to correct tainted water until long after the tainted water has been consumed or used.
In addition, the transmission of water-borne diseases remains a major concern despite worldwide attempt to curb the problem. This problem is not confined to developing and under developed countries but is global in nature. Some key reasons for this are:    (1) The current testing frequencies are not sufficient to provide early warning so that corrective action can be taken to prevent outbreak of diseases; and    (2) The current testing methods are laborious and time consuming and hence discourage frequent testing.
In 1988, Edberg S. C., et al. developed a new technology based on a chemically defined substrate MTF method known as ‘Autoanalysis Colilert (AC): “National filed evaluation of a defined substrate method for the simultaneous evaluation of total coliforms and Escherichia coli from drinking water comparison with standard multiple tube technique’, Appl. Environ. Microbiol., 54 1595 (1988).” This allowed the simultaneous detection and identification of both total coliforms and E. coli in water at 1 CFU per 100 mls in less than 24 hours. The Colilert®, a chromogenic-fluorogenic reagent medium, provided the specific nutrients, and enzyme substrates with chromophores and fluorophores for the simultaneous detection of total coliform and E. coli. In 1989, the US EPA approved this method as a means of qualitative testing of total coliform in drinking water.
The development of chromogenic/fluorogenic reagents to conduct microbial testing has opened the door to better and faster testing protocols. In addition, these products provide the additional opportunity to use technology such as optical spectroscopy to conduct biological, microbiological and chemical analysis. Spectrophotometric analyses are very sensitive and hence can detect the presence of a very low concentration of color producing components of interest in liquid samples (in parts per million). Visually, the human eye can only detect the color when these components are present in very high concentration, thus the need for incubation periods ranging from 18 to 72 hours. The time required to identify or estimate the presence of microbiological indicators in water, food and environmental samples can be drastically reduced when combining incubation with photometric analysis.
The use and advantage of spectrophotometric application to microbial analysis in liquid samples have been cited in the literature. However, the tests have been done outside the incubation chamber by drawing an aliquot of a sample from the incubation vessel to photometric tubes at various intervals and measuring using standard spectrometers. This is not only time consuming but requires separate incubators, spectrometers and technical personnel to conduct the test and in some cases robotic sampling systems. There is also a potential risk of cross contamination and human error, if proper care is not applied in conducting the analysis.
Accordingly, there is an urgent need for improved methods and apparatus for testing microbiological materials in drinking water, recreational water and wastewater, to provide better management of water facilities and to protect public health and the environment.